Page   1
    PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS   ST ScI Use Only
                                                       ID 5488
                                                       Report Date: 18-Jul-95:17:31
                                                       Version: **********
                                                       Check-in Date: **********

1.Proposal Title:
MEASUREMENT OF THE COSMOLOGICAL DEUTERIUM TO HYDROGEN  ABUNDANCE RATIO (CYCLE 4,
HIGH)
------------------------------------------------------------------------------------
2. Scientific Category   3. Proposal For  4. Proposal Type        5. Continuation ID
QUASARS & AGN               GO                                       <none>
Sub Category
QUASAR ABSORPTION
------------------------------------------------------------------------------------
6. Principal Investigator   Institution                    Country    Telephone
 David R. Tytler            UNIVERSITY OF CALIFORNIA AT    USA

------------------------------------------------------------------------------------
7. Abstract
We propose to directly measure the primordial Deuterium/Hydrogen (D/H) abundance
ratio in one QSO absorption system by observing the Lyman Alpha line with the GHRS
(G270M). The D/H ratio is in principle the best measure of the cosmological baryon
to photon ratio (ETA), which leads to the baryon mass density, a critical parameter
which tests the Big Bang model. Solar system and local interstellar measurements of
D/H are highly uncertain (factor of 10) because of chemical fractionation, line
blending and destruction of D in stars. Selected QSO absorption systems should be
free of all these uncertainties, giving a direct, high precision measurement. During
the past decade we have been searching for suitable systems, which must have high HI
column density N(HI) and extraordinarily low velocity dispersion (b). The one
absorption system which we propose to observe is the only one that we know of. It is
a Lyman-Alpha forest cloud (primordial gas) with log N(HI)=17.17 +/- 5% towards
Q1718+481. If primordial D/H=10(-4), the best guess, our error on D/H would be 30%
(+/- 15% on ETA). If D is not detected, our 95% confidence upper limit would be
1.9x10(-5) (barely consistent with corrected local measurements).
------------------------------------------------------------------------------------
------------------------------------------------------------------------------------
9. Est obs time (hours) pri: 4.83     par: 0       10. Num targs pri: 1      par: 0
------------------------------------------------------------------------------------
11. Instruments requested:  HRS
------------------------------------------------------------------------------------
------------------------------------------------------------------------------------
                                                                  Page   2
I. GENERAL FORM    Proposal 5488
PI:  David R. Tytler
Proposal Title:
MEASUREMENT OF THE COSMOLOGICAL DEUTERIUM TO HYDROGEN  ABUNDANCE RATIO (CYCLE 4,
HIGH)
------------------------------------------------------------------------------------

1. Proposers:
Proposers                        Institution                       Country       ESA
------------------------------------------------------------------------------------
Pi David R. Tytler               UNIVERSITY OF CALIFORNIA-SAN      USA
                                 DIEGO
 Xiaoming Fan                    UNIVERSITY OF CALIFORNIA-SAN      USA
                                 DIEGO
 Kenneth M. Lanzetta             UNIVERSITY OF CALIFORNIA-SAN      USA
                                 DIEGO
 Limin Lu                        UNIVERSITY OF WISCONSIN-MADISON   USA
 Blair D. Savage                 UNIVERSITY OF WISCONSIN-MADISON   USA
 Arthur M. Wolfe                 UNIVERSITY OF CALIFORNIA-SAN      USA
                                 DIEGO
                                                                  Page   3
------------------------------------------------------------------------------------
  3. Description of proposed observations.
  The GHRS spectrum of the Lyman-Alpha line at absorption system zabs=0.703
 towards Quasar Q1718+4807 will be carried out with G270M at 2043-2120 Angstroms.
 The Small Science Aperture (SSA) will be used to guarantee the resolution
 (FWHM=15 km/s) needed to resolve the DI and HI lines. VALIDATION ERROR We choose
 to use G270M at 2082A central wavelength. This is unusual, because it is below
 its usual minimum of 2200A, and this causes a validation error. We asked Dennis
 Ebbets about this validation error. He does not know why it ocurrs, but he does
 known that there is no problem taking data at 2082 with G270H, and that the
 spectrum does fall on the detector. G270M IS MORE EFFICIENT THAN G00M AT 2082A.
 We choose G270M rather than G200M because we believe that G270M gives about 2
 times the flux. There are two reasons why be believe this: 1. Blaire Savage has
 GTO spectra of star U-Columbae with both G200M and G270M, both covering 1950-
 2200A. These spectra show that G270M gives twice the signal at 2082A. We do not
 believe that this is an aperture centering problem, though this needs to be
 checked.    2. The pre-launch calibration of the gratings (e.g. HRS Inst Handbook
 Oct 1985, p.38) gave the same factor of two advantage to G270M at 2082A. However
 we are aware that other data contradict this result, and suggest that G200M is
 better. The calibrations in the current instrument handbook, are taken from the
 SV report. On p.6-9 of the ``Final Report of the Sci. Verification Program, 24
 Feb 1992'' there are efficiency curves which give: item
 G200M      G270M efficiency  E from p.6-9      9.6e11     9.7e11 Ang/diode at
 2082             0.0766     0.0966 efficicy per Angstrom         1.27e13
 0.95e13 We asked Steve Hulbert (STScI 410-338-4911) about these, and he gave
 similar numbers (9.7e11 for G200, and 9,2e11 for G270M) on Sept 28 1993. Blaire
 Savage (608 262 2395), Dennis Ebbets (Ball Aerospace, Boulder 303-939-4000x5964)
 and Rich Robinson (GHRS, Goddard) have looked into this and find that we are
 correct, G270 is 2 times faster, and the SV numbers are wrong. We will report
 this to Steve Hulbert.    A second difference between G200M and G270M is
 resolving power. At 2082A, G270M has a slightly lower resolution of R=20,000,
 compared to 24,000 with G200M. (the Sci. Verification Manual page 7-9). We MAY
 change to the LSA if we change to the G200M. Depends on the resolution and how
 well we will know the psf and wavelength scale.   Our IUE spectrum of Q1718+4807
 shows a flux F=1.5 x 10^(-14) ergs/s/cm^2/A at the wavelength of the Lyman-Alpha
 line (2070A). The sensitivity of G270M with the LSA is twice that of G200M at
 that wavelength, E=2x9.5x10^(11) cts/sec/diode at 2070A. Taking into account the
 factor of 2/3 deduction in sensitivity when the SSA is used, the signal count
 rate of 0.020 cts/sec/diode is two times the background of 0.01 cts/sec/diode.
 Thus 5.02 hours is needed to reach the desired S/N=15 per diode. All measurements
 will be carried out with a substep pattern of 2 samples per diode. Standard FP-
 SPLIT will be used in order to reduce detector window and photocathode fixed
 pattern noise. The total spacecraft time is estimated to be 6.88 hours using the
 phase I resource estimator. We will follow recommended observation procedures to
 use LSA with a 5x5 spiral search area (search-size=5) for initial onboard
 acquisition of our target. After initial acquisition, we will use ACQ/PEAKUP for
 both LSA and SSA respectively to more precisely center the object in the
 aperture. Then we take an IMAGE of the field to confirm that the telescope has
 centered our target properly in the dark-taking aperture before our final real
 exposure.
                                                                  Page   4
------------------------------------------------------------------------------------
  4. Justification of need for HST observations.
  HST observations are required because the redshift of the target absorption
 system places the Deuterium and Hydrogen Lyman lines in the UV. We must observe
 low redshift absorbers for the following reasons: (1) Blending is a major problem
 at high z. This is clearly shown in Figure 2, where we show three REAL spectra,
 each with the same resolution and velocity coverage (as seen from a Lyman-Alpha
 line in the middle of each spectrum). Note that blending  remains serious at HST
 wavelengths around 2800A (middle panel), but is much less a problem at our chosen
 wavelengths (bottom panel). This marked change is partially due to the evolution
 of the Lyman-Alpha forest. It is also due to the number of metal lines. A metal
 line systems can have many lines in the UV, so the total number of lines in a
 spectrum scales with the integrated number of systems between us and the QSO,
 which is about (1+zem)^2. (2) The worst sort of blending is that with components
 of the very system under study. Systems at low  z <= 1 are simpler, with fewer
 velocity components, and (or) lower Doppler parameter b values, than those at
 moderate to high z (Boisse etal 1992, Steidel & Sargent 1992).   (3) Our goal is
 to measure primordial D/H much more precisely than has been deduced from local
 ISM data, and the most accurate and reliable D/H measurements must come from the
 lowest z systems, for the above two reasons. (4) We have been searching for
 suitable ground based targets absorption systems for three years now, with no
 success. We frequently find systems which look promising at the start, but when
 we obtain more, higher resolution data, we invariably find that they have more
 velocity components, and so are much less likely to yield a clean D/H
 measurement. We now all agree that it is unlikely that a believable result will
 be obtained with a 4-m telescope. The Keck should be able to measure D/H because
 it can (i) get much higher S/N, and (ii) do many more targets, which will be
 fainter because we have ruled out nearly all known QSOs with magnitude V <= 18.
 But we stress that the two HST targets are much better than any known Keck
 targets. D/H measurement is of sufficient cosmological significance that
 consistent measurements in many systems will ultimately be required to give a
 reliable, high precision value. We expect that this effort will be continued for
 years to come (c.f. Hubble constant, microwave background). There are many
 reasons why an individual system could give a misleading D/H (line blends,
 unobserved velocity substructure,   non-gaussian velocities, stellar processing
 etc.). Candidates for D/H measurement are sufficiently rare, that measurements
 should be attempted in all apparently favorable cases.
------------------------------------------------------------------------------------
  5. Description of special scheduling requirements.
  No request for special scheduling or real-time observations. Note that we do
 request an image with GHRS prior to the exposure, to confirm that the target is
 in the aperture.
------------------------------------------------------------------------------------
  6. Description of special calibration exposures.
  We request a PT-LAMP exposure be obtained immediately after the science
 observation. This is necessary because the proposed scientific analysis requires
 comparison of absorption velocities between different ion species. Therefore,
 accurate wavelength calibration is crucial to our final result.
------------------------------------------------------------------------------------
  8. Additional comments or special requests.
  Our observations use the G270M grating at wavelength around 2070 A (which is not
 generally recommended). We have direct evidence that the G270M can be used at
 2000<lambda<2200 A, and is actually 50-100% more sensitive than the G200M grating
 in this wavelength region. The issue has been discussed with the GHRS scientists,
 and our choice was considered OK.
                                                                  Page   5
------------------------------------------------------------------------------------
  9. Description of previous HST work.
  9. Have you (or your collaborators) received any previous HST observing time or
 archival data?  If so: a. List HST program numbers and titles, and present
 authors involved in each 1162 Interstellar Abundances Toward Extreme Depletion
 Sight Lines: Savage & Cardelli. 1165 and continuation 3960, 4094 Spectroscopy of
 Milky Way Halo Gas: Sarvage, Sembach, & Cardelli. 2257 Physical conditions in the
 gaseous galactic halo: Savage, Cardelli and Edgar. 2424 Quasar absorption line
 survey: Bahcall etal (includes Savage & Wolfe) 2593 White dwarf stars: Shipman et
 al (include Tytler). 3463 HIghly Ionized Nitrogen in the Galactic Halo: Savage,
 Sembach,& Lu 3801 and continuations 4107, 4969. QSO Suitable for the Observation
 of HeII 304: Tytler, Lanzetta, Fan, & Turnshek. 4342 Damped Lyman Alpha Systems
 in IUE Spectra: Lanzetta, Wolfe & Turnshek. 4396 and continuations 4952, 4953.
 QSO Absorption System Sanp Shot Survey: Tytler, Lanzetta, Fan & Bowen.   b.
 Specify which of the above programs are related to this proposal and summarize
 the scientific relationship, completion status, and main results from each. None
 of the above programs is related with the current proposal. Not data has been
 obtained from program 4324. GTO1165 has produced Echelle data for HD 167756, a
 star in the low halo (scale height about 0.8 kpc). These measurements of Si IV, C
 IV and N V are of high quality and reveal important similarities and differences
 in the line profiles among the highly ionized species. The measurements imply the
 sightline contains at least two types of highly ionized gas. One type at high
 temperature produces the smooth N V profile and the  other type at intermediate
 temperature produces the structured Si IV profile. A paper has been submitted to
 ApJ. GTO4094 has just resulted in the detection of very strong N V absorption
 associated with the outer Galaxy in the direction of H 1821+643 (see illustration
 in figure 1). GO2257 has produced intermediate resolution spectra of high and low
 ionization lines toward two Galactic stars in the halo. One is toward the north
 Galactic pole and the other toward the south Galactic pole.   In each case
 absorption by N V is detected. A publication reporting on the absorption by the
 highly ionized gas is currently in preparation. GO2424 has produced FOS spectra
 of a large number of Quasars at low and moderate redshift in order to study the
 intergalactic medium and the ISM of intervening galaxies. Approximately 50% of
 the absorption lines seen in these spectra arise in the Milky Way. The first
 series of papers reporting results for the IGM and Milky Way is in press (see
 publication list). The Milky Way data reveal the detection of metal line analogs
 to the high velocity cloud phenomena, provide information on the scale height of
 interstellar C IV, and permit the comparison of absorption by the Milky Way halo
 with absorption seen in the low and intermediate redshift Universe. GO3463 has
 produced intermediate resolution GHRS spectra for NGC3783 revealing the existence
 of strong absorption by N V and C IV in the Milky Way halo in the direction
 l=278 degrees and  b=+23 degrees. In addition, the spectra provide the first
 reliable estimate of the abundance of an undepleted element (sulfur) in a high
 velocity cloud (v = 240 km/s).  The results of this work are nearly ready for
 submission by Lu, Savage, & Sembach.   Programs 3801, 4107 & 4969 have yielded
 about 80 images of QSO fields. We detected two QSOs, which agrees with
 expectation, and have places flux limits on the others. This work is reported in
 full in a follow-up cycle 4 proposal. Programs 4396, 4952 & 4953 have generated
 55 spectra. c. List publications resulting from the above data (Format: Title,
 Authors,Journal, Volume, Page, and Year.) Optical HST GASP Positions and FInding
 Charts for Bright Quasars from the HST FOS 'QSO Absorption System Snap Shot
 Survey', Bowen, Osmer, Tytler, Cottrell, Fan, Lanzetta, submitted to AJ, 1993.
 First Results from the GHRS: Elemental Abundances as a Function of Velocity  in
 the Neutral Gas toward Xi Per, Savage, Cardelli, Bruhweiler, Smith , Ebbets &
 Sembach, ApJ, 377, L53, 1991 First Results from the GHRS: Elemental Abundances in
 the Diffuse Clouds toward Xi Per, Cardelli, Savage, Bruhweiler, Smith, Ebbets,
 Sembach & Sofia,  ApJ, 377, L57, 1991   First Results from the GHRS: Interstellar
 C I, S I, and CO toward Xi Per, Smith, Bruhweiler, Lambert, Savage, Cardelli,
 Ebbets, Lyu Sheffer,  ApJ, 377,  L61, 1991 First Results from the GHRS: The
 Galactic Halo and the Lyman-Alpha Forest at Low Redshift in 3C 273,  Morris,
 Weymann, Savage & Gilliland,  ApJ, 377, L21, 1991 Gas Phase Abundances of C, O,
 N, Cu, Ga, Ge, and Kr Toward Zeta Oph, Cardelli, Savage & Ebbets, ApJ, 383, L23,
 1991 UV Observations of the Gas Phase Abundances in the Diffuse Clouds Toward
 Zeta Oph at 3.5 km/s Resolution, Savage, Cardelli & Sofia, ApJ, 402, 706, 1992
 Abundance of  Interstellar Carbon Toward Zeta Ophiuchi , Cardelli, Mathis, Ebbets
 & Savage, ApJ, 402, L17, 1993 Observations of the Gaseous Galactic Halo Toward 3C
 273 with the GHRS, Savage, Lu, Weymann, Morris & Gilliland,  ApJ, 404, 124, 1993
 Observations of 3C273 with the GHRS on the Hubble Space Telescope Brandt et al.
 (including Savage and Lu),   AJ, 105, 831, 1993 High Resolution Ultraviolet
 Observations of the Interstellar Diffuse Clouds Toward Mu Columbae, Sofia, Savage
 & Cardelli, ApJ, in press, 1993 The HST Quasar Absorption Line Key Project I.
 First Observational Results, Including Lyman Alpha  and Lyman Limit Systems,
 Bahcall etal (including Savage, Wolfe),  ApJS, 87, 1, 1993 The HST Quasar
 Absorption Line Key Project II. Data Calibration and Absorption Line Selection,
 Schneider etal (including Savage, Wolfe), ApJS, 87, 45, 1993 The HST Quasar
 Absorption Line Key Project  III. First Observational Results on Milky Way Gas,
 Savage etal, (including Lu \& Wolfe), ApJS, in press, 1993 Highly Ionized Gas
 Absorption in the Disk and Halo Toward HD 167756 at 3.5 kilometers per Second
 Resolution, Savage, Sembach & Cardelli, ApJ, submitted, 1993   Al III, Si IV, and
 C IV Absorption Toward Zeta Ophiuchi: Evidence for Photoionized Gas and
 Collisionally Ionized Gas, Sembach, Savage & Jenkins, ApJ, submitted, 1993
                                                                  Page   6
------------------------------------------------------------------------------------
 10. Resources to be supplied by investigator's institution(s).
  10. Resources to be supplied by your institution(s) in support of this project
 (e.g. data-analysis capabilities, research assistance, students, funds). UCSD has
 one of the largest groups in the world working on QSOs and especially absorption
 lines: 5 faculty, 2 research scientists, 2 postdocs, 7 graduate students and 3
 undergraduates. We are also the home institution for the FOS. We have 1 Sun
 sparcstation-1, and 1 sun-360 and one Sun IPX which could be used for this
 proposal. We also have 3 Sun SLC work stations which lack imaging capability. We
 have a large amount of relevant software. We have regular access to Lick, and
 hopefully the Keck observatory, where we will obtain observations of the QSO
 targets. We receive partial funding (air ticket only) from the university for
 observing trips at Lick. Money is available to support special (minority)
 undergraduates. The University of Wisconsin-Madison will provide the necessary
 data handling and analysis facilities through a network of high-power and through
 the Midwest Astronomical Data Reduction and Analysis Facility.
------------------------------------------------------------------------------------
11. Address Information
Name:  David R. Tytler                                     Category: PI
Institution: 1560 - University of California,
Address:  CASS, 0111
          UNIVERSITY OF CALIFORNIA AT SAN DIEGO
City: La Jolla                                  State: CA
Zip Code: 92093                                 Country: USA
Telephone: (619) 534-7670
Telex (or e-mail):
------------------------------------------------------------------------------------
TARGET LIST    a) Fixed Targets                                                                    ID = 5488             [  7]
------------------------------------------------------------------------------------------------------------------------------------
 1 |     2      |           3           |              4             |  5     |   6    |  7  |              8
------------------------------------------------------------------------------------------------------------------------------------
Tar|   Target   |         Target        |            Target          |Coord   | Radial |Acqui|FLX|     Flux data
No |    Name    |       Description     |           Position         |Eqnx    |  Vel.  |Prblm|REF|
   |            |                       |                            |        |        |     |   |
------------------------------------------------------------------------------------------------------------------------------------
101 QSO-         E,313,                  PLATE-ID=02D4,               J2000    ZEM=           1   V = 15.0 +/- 0.5
    171938+48041 H,515,519               RA = 17H 19M 38.25S +/-               1.084          2   F-CONT(2070)=1.5 +/- 0.3 E-14
    2 QSO-                               0.1S,
    1718+4807                            DEC = +48D 04' 12.50" +/-
    QSO1718+481                          1.0"
     Comments: GO REF. Q1718+4807 FOR D/H MEASUREMENT
------------------------------------------------------------------------------------------------------------------------------------
EXPOSURE LOGSHEET                                                                                  ID = 5488             [  8]
------------------------------------------------------------------------------------------------------------------------------------
 1      |   2   |      3    |  4   |   5   |   6   |    7   |   8   |       9       |10 |   11  |   12    |13 |14|        15
------------------------------------------------------------------------------------------------------------------------------------
  Line  |  Seq  |   Target  |Instr | Oper. | Aper  |Spectral|Central|   Optional    |Num|  Time |   S/N   |Flx|Pr|     Special
 Number | Name  |    Name   |Config| Mode  |or FOV |Element |Waveln.|  Parameters   |Exp|       |Rel. Time|Ref|  |   Requirements
------------------------------------------------------------------------------------------------------------------------------------
201              QSO-        HRS    ACQ     2.0     MIRROR-N2        SEARCH-SIZE=5   1   100S              1   1  ONBOARD ACQ FOR
                 171938+4804                                         BRIGHT=RETURN                                202
                 12                                                                                               CYCLE 4
     Comments: SETP-TIME=4S EXPECTED COUNT
               RATE FOR N2: 1400 C/S
------------------------------------------------------------------------------------------------------------------------------------
202              QSO-        HRS    ACQ/    2.0     MIRROR-N2                        1   204S              1   1  ONBOARD ACQ FOR
                 171938+4804        PEAKUP                                                                        203
                 12                                                                                               CYCLE 4
     Comments: SETP-TIME=2S
------------------------------------------------------------------------------------------------------------------------------------
203              QSO-        HRS    ACQ/    0.25    MIRROR-N2                        1   50S               1   1  ONBOARD ACQ FOR
                 171938+4804        PEAKUP                                                                        204-206
                 12                                                                                               CYCLE 4
     Comments: SETP-TIME=2S
------------------------------------------------------------------------------------------------------------------------------------
204              QSO-        HRS    IMAGE   0.25    MIRROR-N2        NX=16           1   256S              1   1  CYCLE 4
                 171938+4804                                         NY=16
                 12
     Comments: TAKE MAP AFTER CENTERING STEP-
               TIME=1S
------------------------------------------------------------------------------------------------------------------------------------
205              QSO-        HRS    ACCUM   0.25    G270M    2073    STEP-PATT=4     14  20.7M   15        2   1  CYCLE 4
                 171938+4804                                         FP-SPLIT=STD                301.5M
                 12                                                  DOPPLER=DEF
------------------------------------------------------------------------------------------------------------------------------------
206              WAVE        HRS    ACCUM   SC2     G270M    2073                    1   1M                    1  CALIB FOR 205 NO
                                                                                                                  SLEW
                                                                                                                  GROUP 205-206 NO
                                                                                                                  GAP
                                                                                                                  CYCLE 4
------------------------------------------------------------------------------------------------------------------------------------
            Summary Form for Proposal 5488                                                                               [  9]

  Item                          Used in this proposal
------------------------------------------------------------------------------------------------------------------------------------
  Configurations                HRS
------------------------------------------------------------------------------------------------------------------------------------
  Opmodes                       ACQ ACQ/PEAKUP IMAGE ACCUM
------------------------------------------------------------------------------------------------------------------------------------
  Optional Parameters           SEARCH-SIZE=5 BRIGHT=RETURN NX=16 NY=16 STEP-PATT=4 FP-SPLIT=STD DOPPLER=DEF
------------------------------------------------------------------------------------------------------------------------------------
  Proposal for                  GO
------------------------------------------------------------------------------------------------------------------------------------
  S/C Hours                     4.83
------------------------------------------------------------------------------------------------------------------------------------
  Scientific Category           QUASARS & AGN
------------------------------------------------------------------------------------------------------------------------------------
  Scientific Sub-category       QUASAR ABSORPTION
------------------------------------------------------------------------------------------------------------------------------------
  Special Requirements          ONBOARD ACQ FOR 202; CYCLE 4; ONBOARD ACQ FOR 203; ONBOARD ACQ FOR 204-206; CALIB FOR 205 NO SLEW;
                                GROUP 205-206 NO GAP;
------------------------------------------------------------------------------------------------------------------------------------
  Spectral Elements             MIRROR-N2 G270M
------------------------------------------------------------------------------------------------------------------------------------
  Target Names                  QSO-171938+480412 QSO-1718+4807 QSO1718+481
------------------------------------------------------------------------------------------------------------------------------------